Climate: Early plants may have triggered ice ages

The emergence of land plants may have dramatically shifted the Earth's climate about 470 million years ago.

Emergence of mosses tilted Earth’s carbon balance

By Summit Voice

SUMMIT COUNTY — The emergence of primitive plants some 470 million years ago had a profound impact on the climate of the Earth. As they weathered the rocks they grew on, the plants released calcium and magnesium ions, removing carbon dioxide from the atmosphere.

The same weathering process resulted in massive quantities of iron and phosphorus reaching the oceans and fueling productivity and resulting in even more carbon being absorbed from the atmosphere.

Altogether, the emergence of plants — ancestors of mosses still growing today — may have caused temperatures to drop by up to 8 degrees celsius, triggering a series of ice ages during the Ordovician period, according to new research by scientists at the universities of Exeter and Oxford. Their study was published Feb. 1 in Nature Geoscience.

“This study demonstrates the powerful effects that plants have on our climate,” said Tim Lenton, of the University of Exeter. “Although plants are still cooling the Earth’s climate by reducing atmospheric carbon levels, they cannot keep up with the speed of today’s human-induced climate change. In fact, it would take millions of years for plants to remove current carbon emissions from the atmosphere,” he said.

“For me the most important take-home message is that the invasion of the land by plants – a pivotal time in the history of the planet – brought about huge climate changes,” said Professor Liam Dolan of Oxford University. “Our discovery emphasizes that plants have a central regulatory role in the control of climate: They did yesterday, they do today and they certainly will in the future,” he said.

The team used the modern moss, Physcomitrella patens for their study. They placed a number of rocks, with or without moss growing on them, into incubators. Over three months they were able to measure the effects the moss had on the chemical weathering of the rocks.

They then used an Earth system model to establish what difference plants could have made to climate change during the Ordovician Period.